INFLUENCE OF TEMPERATURE AND WATER-VAPOR PRESSURE DEFICIT ON SURVIVALOF FRANKLINIELLA-OCCIDENTALIS (THYSANOPTERA, THRIPIDAE)

The influence of temperature and vapor pressure deficit (VPD) were det ermined on larval, pupal, and adult stages of nonfeeding Frankliniella occidentalis (Pergande) under controlled laboratory conditions and on first instars confined to cucumber leaves under controlled greenhouse conditions. The influence of temperature and VPD on sanitation clean- up for control of thrips at the end of the growing season in the green house was also determined. In laboratory trials, the larval stages exh ibited the lowest percentages of survival under the range of temperatu res and VPDs tested. The adult stage had >80% survival except with hig h VPDs at 25, 30, and 35-degrees-C. Pupae had 100% survival at all tem peratures except 35-degrees-C, at which survival decreased to almost-e qual-to 60% at the higher VPDs. A quadratic model was fitted to the re sponse surfaces of the larval and adult stages. By using the quadratic model, it is possible to predict the response of the different stages of F. occidentalis to a range of hygrothermal conditions. Cage trials of first instars on cucumber leaves in the greenhouse also showed tha t high temperature and VPD will decrease the percentage survival of F. occidentalis. Sanitation trials demonstrated that 40-degrees-C and VP D greater-than-or-equal-to 4.76 kPa will control F. occidentalis at th e end of the crop season when the greenhouse is being prepared for the next crop.